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Patented July 16,

Ira/anion G H ARNOLD TELEPHDNIO REPEATING CIRCUIT AND APPARATUS. No. 542,619.

' NITED STATES PATENT OFFICE.

CHESTER H. ARNOLD, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE AMERICAN BELL TELEPHONE COMPANY, OF SAME PLACE.

.TELEPHONIC REPEATING CIRCUIT AND APPARATUS.

SPECIFICATION forming part of Letters Patent No. 542,619, dated July 16, 1895.

Application filed March 16, 1895- Serial No. 542,060 (No model.)

To aZZ whom it may concern.-

Be it known that I, CHESTER H. ARNOLD, residing at Boston, in the county of Sufiolk and State of Massachusetts, have invented certain Improvements in Telephonic Repeating Circuits and Apparatus, of which the fol lowing is a specification.

When two telephone main circuits are united by link conductors at a central station they virtually constitute a single main circuit extending between two terminal stations and the said central station becomes an intermediate station of such a line. Such a compound circuit may therefore be regarded either as one long circuit or as two independent circuits joined together for through communication. When the circuit so formed is very long-say over one thousand miles in length the currents developed in it by the operation of the transmitter at either terminal station are liable to considerable dissipation in traversing the line, and as a consequence the speech is but imperfectly reproduced by the receiver at the other end. In consideration of such inefficient operation of the receiver it is desirable to provide a relay or repeating apparatus atsome convenient intermediate station about the middle of the compound line, which shall be actuated by the relatively unweakened current flowing in a circuit of approximatelybut half of the total length of the said compound line, and which when so operated shall be capable of reinforcing the workingcurrent by throwing upon the circuit a renewed current, due to a fresh source of electrical energy.

My invention proposes to provide such an apparatus, and to combine the same with a compound circuit of the above-mentioned character and constitution, and it comprehends a relay or repeating-magnet in a bridgecircuit controlling the resistance of a local repeating-circuit, which in turn reacts upon the main line through the intermediation of one or more induction-coils, and thereby reinforces the original current by bringing into play a new one supplied by a fresh and independent generator contained in the said local circuit. The primary winding of the induction-coil is included in the said local circuit and the secondary winding is placed the two sides of the bridge connection respectively.

The characteristic feature, however, of my invention is that the repeating-magnet has no conductive connection with the main tele phone circuit or circuits, and that its connection therewith is purely inductive, a condenser or condensers being interposed between main circuit and the bridge containing the said magnet. The said condensers may be of the ordinary or standard form, and they may be inserted one between each end of the bridge connection and the through circuitconductors, the latter being without breach of continuity at the repeating-station, or they may be constructed by severing the continuity of the main conductors at the repeating-station and'byconnecting both ends of the bridge with relatively short parallel conductors running parallel with the said main conductors, in close inductive proximity thereto, but separated therefrom by a suitable dielectric.

Figure 1 is a diagram of the connections of a balanced reinforcing relay or repeater applied to a compound telephone-circuit, the condenser employed. being of the ordinary or standardtype; and Fig. 2 is a similar dia tions A and B the usual telephone apparatus is placed, but for the purposes of this invention it is only necessary to show thetransmitter local circuits E, containing the variable transmitters m, and their sources of current I) (ordinarily batteries) and the receivingtelephones T included in the main-line circuit,

an induction-coil I being also provided in a manner well understood and interposed between the local and main circuits, its coarse and short wire primary winding being in cluded in the said local and its long and fine wire secondary winding being included in sequence with the receiving-telephone in the main circuit. The two main circuits L and L being formed at the repeating-station G into one long-talking circuit, as shown, a repeating apparatus is associated with the said conjoint-circuit in the following manner: At the said repeating-station C an elec- I magnet.

The variable-resistance medium M of a repeating or reinforcing transmitter is mounted immediately in front of'the armature or diaphragm of the repeating-magnet in position to be operated or controlled thereby, and the said variable resistance is placed in a local repeating-circuit F of a reinforcing-generator or source of current 6 which local circuit, traceable through the numerals 4, 5, 6, and 7, likewise contains the primary winding of an induction-coil 1 which has its windings both centrally divided into two sections. One section .9 of the secondary winding of the said induction-coil I is placed in the main conductor 2 on one side of the bridge-junction 0c; and the remaining section thereof is placed in the main conductor 3 on the other side of the bridge-junction 1 These windings are so disposed in order that a more accurate balance may be maintained, and it is obvious that the two sections are to be so wound or electrically connected that the currents generated in them by the action of the relay apparatus will be coincident in direction in the main conductors but opposite in direction through the bridge (1, whereby the repeatingniagnet R in the said bridge is free from any disturbing effects from the repeater-current while remaining fully subject to the control of currents due to the operation of the transmitters m at the distant stations A and B.

In Fig. 2 the connections and appliances are the same as in Fig. 1, and the sole difference consists in the construction and arrangement of the inductive bridge-circuit d. In it, instead of employing condensers of the ordinary and standard form, I elect to employ condensers based on a principle which has heretofore to some extent been used in cables, and

which is fully described and illustrated in Letters Patent of the United States, No. 469, l75, granted to Hammond V. Hayes and John S. Stone, February 23,1892, wherein the two opposing plates,members,orsurfaces of the condenser are formed of two independent parallel conductors and are separated conductively from one another by an interposed layer or strip of suitable non-conducting material of high specific inductive capacity constituting the dielectric, but held in close inductive relation through the instrumentality of the same interposed non-conductor.

The main conductors 2 and 3 are severed at o and w, and auxiliary conductors c 0 overlap the gap or space thus made and extend for some distance parallel to the main conductors on both sides thereof, being separated therefrom by a suitable partition of any suitable insulating material. The parallel portions of the main conductors and of the gapspanning conductors thus constitute the opposing condenser-plates.

The bridge d, containing the repeating-magnet R, unites points a: and y of the conductors o and 0 respectively, and the secondary winding-sections s and s of the repeater induction-coil I are placed one on each side of the bridge, also in the gap-spanning conductors 8' .9

It will be observed that in both exemplifications of this invention the repeating-magnet has no conductive connection with the main circuit and that the original voice-currents act thereon by electrostatic induction, or by what has been called admittance condensers, suitably proportioned to the circuits, being, so to speak, transparent with respect to voice-currents. In Fig. 2, moreover, the same process is relied upon also for the maintenance of such communication as occurs between the severed portions of the two main conductors direct, as well as from either to the bridge and from the repeater to the receiving end of the main circuit.

Experience indicates that the employment of these forms of repeater results in a considerable amplification or reinforcement of vol ume.

I claim- 1. In a telephone circuit repeating system, the combination of a main telephone circuit; a local repeating circuit containing a source of current and a variable resistance repeating transmitter; a repeating or receiving electromagnet in a bridge having electrostatic or inductive electrical connection between the conductors respectively of said main circuit; placed in operative relation to the said repeating transmitter to actuate the same; and a repeating induction coil having its secondary winding divided into two sections, placed respectively at the two ends of the bridge and on different sides thereof, and provided with a similarly divided primary whose sections are both included in the local IIO circuit, and each associated with one of the said secondary sections; substantially as described.

2. In a telephone circuit repeating system the combination substantially as hereinbefore described, of a main telephone circuit; a local repeating circuit containing a variable resistance transmitting medium, and a source of current; a bridge conductor extending between the conductors of the said main circuit, and containing a repeating or receiving electromagnet mounted in operative relation to the said variable resistance medium and adapted to operate the same; a condenser interposed in the said bridge whereby it is divided conductively, but left inductively continuous; and a repeating induction coil interposed between the local and main circuits, having its secondary windings in two sections placed in the main line conductors respectively, one on each side of the bridge, and its primary also in two sections placed in the 10- cal circuit, and associated each with one of the secondary sections.

3. The combination in a telephone circuit repeating system, of a main telephone circuit; a local repeating circuit including a variable resistance transmitting medium; a bridge extending between the main circuit conductors; a repeating or receiving electro in agnet mounted in operative relation to the said variable resistance medium; and a repeating induction coil having its secondary winding in two-sections connected in the two main line conductors on different sides of the bridge, and its primary also in two sections both in the local circuit, and each associated with one of the secondary sections; with two condensers included in the circuit of the bridge conductor one on each side of the repeating electro-magnet; substantially as described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 7th day of March, 1895.

CHESTER H. ARNOLD. lVitnesses:

GEO. WILLIS PIERCE, FRANK C; LOOKWOOD. 

